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Warble tone alarm circuit

2016-02-19 00:34  
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Warble tone is a tone whose frequency varies periodically several times per second over a small range; used to prevent standing-wave patterns from forming in reverberation chambers.The circuit generates a warble-tone alarm signal that simulates the sound of a British police siren. IC1 is wired as an alarm generator and IC2 is wired as a 1 Hz astable multivibrator. The output of IC2 is used to frequency modulate IC1 via R5.The action is such that the output frequency of IC1 alternates symmetrically between 500 Hz and 440 Hz, taking one sound to complete each alternating cycle.The warble tone alternates between a low frequency sound and a high frequency sound. Ultra loud models are available in 2 warble cadences,slow (1 pulse per second) and fast (3 pulses per second).The warble tone alarm is typically used in situations where an important event must be audibly enunciated.
 
Warble-tone alarm